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The role of sf6 gas in silicon nitride etching

Sulfur hexafluoride, a gas with excellent insulation, is often used in high voltage arc extinguishing and transformer, high voltage transmission line and mutual inductor. But in addition to these functions, sulfur hexafluoride can also be used as an electronic etchant. Electron grade high purity sulfur hexafluoride is an ideal electron etcher and has been widely used in the field of microelectronics technology. Today, I will introduce the application of sulfur hexafluoride in silicon nitride etching and the influence of different parameters.

We explore SF6 plasma etching SiNx process, including the change of plasma power, SF6 / He gas ratio and adding electronegative gas O2, discusses its components protective layer for the TFT SiNx etching rate, and by using the plasma emission spectrometer SF6 / He, SF6 / He/O2 plasma concentrations of each species change and SF6 dissociation rate were analyzed, and discuss the changes of SiNx etching rate and the correlation of plasma concentrations of species.

Sulphur hexafluoride cylinders

It is found that the etching rate increases with the increase of plasma power. If the flow rate of SF6 in plasma increases, the concentration of F atom increases and is positively correlated with the etching rate. In addition, when the negative gas O2 is added at a fixed total flow rate, the etching rate will increase. However, under different O2/SF6 flow ratios, there will be different reaction mechanisms, which can be divided into three parts :(1) the O2/SF6 flow ratio is very small, O2 can help the dissociation of SF6, and the etching rate is higher than that without O2. (2) When the O2/SF6 flow ratio is greater than 0.2 to the interval approaching 1, a large number of SF6 atoms are dissociated to form F, so the etching rate is the highest. However, at the same time, O atoms in the plasma are also increasing and easy to form SiOx or SiNxO(Y-X) with the SiNx film surface, while the more O atoms are increased, the more difficult F atoms are to undergo the etching reaction, so when O2/SF6 ratio is close to 1, the etching rate starts to slow down. (3) When the O2/SF6 ratio is greater than 1, the etching rate decreases. Due to the large increase OF O2, the dissociated F atoms collide with O2 and form OF, which reduces the concentration OF F atoms and leads to the decrease OF etching rate. From this, it can be seen that when O2 is added, the flow ratio of O2/SF6 is between 0.2 and 0.8, and the best etching rate can be obtained.

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